A hollow door seal for an automobile (hereinafter referred to simply as a door seal) includes a part provided with a bridge in a hollow portion and a part provided with no bridge in the hollow portion, depending on the mounting position of the door seal.
In an automobile of a hard-top type mounting a door mirror thereon, for example, the door seal is formed by connecting three kinds of door seal parts as shown in FIG. 13 That is, three kinds of door seal parts S'.sub.1, S'.sub.2 and S'.sub.3 having different sectional shapes are independently formed. The door seal part S'.sub.1 and the door seal part S'.sub.2, both constituting a straight front side portion of the door seal where the door mirror is located, are bonded together at a connecting portion A. Further the door seal part S'.sub.2 constituting the front side portion and the door seal part S'.sub.2 constituting an upper side portion of the door seal are corner-molded and connected together at a connecting portion B. The door seal part S'.sub.2 constituting the upper side portion and the door seal part S'.sub.3 constituting a rear side portion of the door seal are also corner-molded and connected together at a connecting portion B'.
The door seal part S'.sub.1 to be mounted at a position where the door mirror is located has no bridge in the hollow portion, so as to reduce the seal reaction generated due to deformation when the door mirror contacts the door seal part S'.sub.1, and thereby ensuring ready fitting of the door mirror with the door seal part S'.sub.1. In contrast, the door seal part S'.sub.2 mounted at a position where a window glass of the door is located has a bridge in the hollow portion, so as to generate a large seal reaction and thereby ensure a high sealability when the window glass comes into contact with the door seal part S'.sub.2. Further, the connecting portion B at the front corner of the door seal is formed of a seal member having the same structure as that of the door seal part S'.sub.1. That is the connecting portion B has no bridge in the hollow portion. Further, lower ends F of the door seal parts S'.sub.1 and S'.sub.3 are end-molded
As mentioned above, the conventional door seal for an automobile mounting a door mirror thereon employs three kinds of door seal parts, and requires corner-molding at two positions and straight-bonding at one position. Accordingly, the number of manufacturing steps in the molding operation is increased, and the connecting portions are visibly perceived to deteriorate the appearance.
It is accordingly an object of the present invention to eliminate the connecting portions by integrally forming a first seal portion having no bridge in the hollow portion and a second seal portion having a bridge in the hollow portion by continuous molding.
According to the present invention for achieving the above object, there is provided a molding method for a seal for an automobile, comprising the steps of separately forming a first extrusion passage for extruding a molding material into a hollow portion of said door seal and a second extrusion passage for extruding a molding material into a bridge in the hollow portion of said seal in an extrusion opening of a molding die with use of a core, axially moving a molding material discharge pipe inserted into said molding die, and repeatedly closing and opening a molding material supply passage communicated with said second extrusion passage so as to intermittently extrude the molding material from said second extrusion passage.
The material to be molded into the body portion of the seal is continuously extruded. However, the material to be molded into the bridge in the hollow portion of the seal is intermittently extruded from the second extrusion passage by repeating the closing and opening of the molding material supply passage as communicated with the second extrusion passage by axial movement of the molding material discharge pipe. Accordingly, the first seal portion having no bridge in the hollow portion and the second seal portion having the bridge in the hollow portion can be continuously molded.
As a result, the connecting portion between the first and second seal portions can be eliminated to thereby improve the appearance. Further, the number of manufacturing steps for the connection between the seal parts necessary in the prior art method can be eliminated to thereby improve the productivity.